Sheet-bending method and machine for the production of tubular elements



Feb. 6, 1962 Filed Jan. 28, 1959 F. H. MONTIG NOT SHEET-BENDING METHODAND MACHINE FOR THE PRODUCTION OF TUBULAR ELEMENTS 2 Sheets-Sheet 1 Feb.6, 1962 F. H. MONTIGNOT 3,019,834

SHEET-BENDING METHOD AND MACHINE FOR THE PRODUCTION OF TUBULAR ELEMENTSFiled Jan. 28, 1959 2 Sheets-Sheet 2 3,019,834 SHEET-BENDING METHOD ANDMACHINE FOR THE PRODUCTION OF TUBULAR ELEMENT Francois HJMontignot,Pont-a-Mousson, France, assignor to Compagnie dc Pont-a-Mousson, Nancy(Menrtheet-Moselle), France, a French body corporate Filed Jan. 28, 195%Ser. No. 789,534 Claims priority, application France Jan. 31, 1958Claims. (Cl. 153-65) The present invention relates to methodsandmachines for bending metal sheets or plates for the production oftubular elements, and more particularly to methods and machines wherebysaid elements are produced by the application of a plane metal sheet onan anvil or like former by a punch imparting successive blows.

An object of the invention is to provide a method of bending a sheet inthe form of a tubular element, said method being improved in such manneras to coil and produce said tubular element without any special devicefor driving said element and without any oscillation of the latter aboutits axis which remains fixed, thereby increasing the precision andregularity of production and prolonging the life of the tool equipment.

In said improved method, which is of the type in which the sheet to bebent is coiled round a former, said sheet is fed to said former in acontinuous manner so that a certain length of sheet is freely located inspace beforereaching the former, and there are applied successively onsaid sheet discontinuous bending blows so as to bend a portion of saidsheet permanently at each blow by applying it against the former on apart of its face on the side of the former adjacent the point from whichthe sheet is fed, so as to create at the same time in said free lengthof sheet in the region of the latter located between the point where itis temporarily stopped from moving due to its application against theformer and the point.

a punch on the portion of the sheet situated immediately on the inputside of the anvil, that is, on the side of the latter nearest the pointfrom which the sheet is continuously fed.

Another object of the invention is to provide a bending machine forbending in accordance with the foregoing method, said machine havin afixed former and a feed device for feeding said sheet to the machine ina continuous manner, the feed device being located at a distance fromthe former which is equal to said free length of the sheet and a bendingdevice being provided for exerting discontinuous successive bendingforces on said sheet along an axis which is offset relative to the axisof the former on the side thereof adjacent the point from which saidsheet is fed.

Further features andadvantages of the invention will be apparent fromthe ensuing description, with reference to the accompanying drawing, towhich the invention is in no way restricted.

In the drawing:

FIG. 1 is a side elevational view, partly in section and partiallybroken away, of a machine according to the invention;

FIG. 2 is an elevational view, partly in section on line 2-2 of FIG. 1;

FIG. 3 is a plan view corresponding to FIG. 2;

FIG. 4 is an enlarged diagram illustrating the method of the invention,and 7 FIG. 5 is a partial view, similar to FIG. 1, of a modification ofthe machine of the invention.

In the embodiment shown in the drawing, the machine is adapted to coilor bend in a helical manner a metal sheet r continuously fed by afeeding device G so as to produce a tubular element T WhOSe helicalcoils are subsequently welded.

Said machine comprises a stand 1, uprights 2 and a table 3. The lattercarries one end 4a of a fixed former having an effective cylindricalouter face having an axis XX and a radius of curvature substantiallyequal to the inside radius of the tubular element T to be produced.

The cross-sectional shape of said former or anvil 4- preferably by aninterchangeable support block of con-.

stant shape and size irrespective of the radius of curvature of theeffective face of the anvil 4 and said block 4a is detachably secured tothe table 3 by a dovetail arrangement (not shown) and a bolt 5. Theattachment of the block 4a to the table 3 is furthermore reinforced byan inverted U-shaped strap 6 provided with a foot 7 fixed to the tableby a dovetail arrangement 8' (FIG. 1). The foot 7 is provided with anaperture 9 (FIG. 2) for passage therethrough of the sheet t when thelatter is fed to the machine, and on the side of the' foot 7corresponding to the effective face of the anvil 4 the foot doesnotextend beyond the support block 4aso as not to obstruct the region wherethe sheet t starts to coil round the anvil.

The table 3 also carries on the opposite side of the anvil to the devicefeeding the sheet to the anvil a guide block 10 whose effective face 11(FIG, 4) is part-cylindrical and has an axis XX and a radius ofcurvature equal to the outside radius of the tube T to be produced. Theblock 10 is fixed to the table 3 by a dovetail arrangement 12 (FIG. 1).

In the region where the sheet t starts to coil round the anvil a thereis mounted a punch 13 whose effective W face 14 (FIG. 4 is convex andwhose strokeaxis Y 'Y is offset relative to the axis X, X of the anvil adistance x toward the region from which the sheet 1 is fed. The two axesare orthogonal. V

The punch 13 is mounted on a plate 15 by a dovetail arrangement 16'andbolts 17 (FIG. 1). The plate is vertically slidable between twoslideways 18 provided on the table 3 and is pivotably connected at 19 toa link and crank arrangement speed reducer unit 23.

Further, a spot-welding device having electrodes 24 2t), 21, 22 drivenby a motorand 25 is mounted on the anvil and the punch and the electriccircuit actuating said device is adapted to supply alternat ng currentto said electrodes in each operative stroke of the punch, said electricsupply circuit being controlled by a contactor 26 (FIG. 1) actuated bythe link and crank arrangement so that a spot weld is formed for eachblow of the punch.

The lateral feed device G which continuously feeds positively and guidesthe sheet I, is so adapted that the sheet is free in space over acertain length L which is about 50 cm. for a 2 mm. thick steel sheet('FIG. 1) be- 7 tween the point at which the sheet leaves said deviceand j the point at which it is tangent to the anvil 4. Saidfeed devicecomprises rollers 27 (FIG. 1) some of which are driving rollers sincethey are connected to a motor-speed reducer unit 28. Although forreasons of clearness the Patented Feb. 6, 1962 feed device 6' is shownin FIG. 1 to have rollers parallel with the axis XX, in actual fact saiddevice G, which is orientatable, is so disposed that the direction f offeed of the sheet If toward the anvil 4 forms an acute angle y with theaxis XX (FIG. 3).

Fixed in opposed relation to one another on the foot 7 are two plungers29 and 30 which are located above and below the sheet 2. respectively,in the region between the feed device G and the bending device. Saidplungers control the opening, in opposition to the action of closingreturn springs 31 and 32, of switches 33 and 34 respectively inserted inthe electric supply circuits 35 and 36 of the motor-speed reducer units28' and 23. Said switches are connected in series with hand controlswitches 37' and 38. The setting of the plungers 29 and 34 will beexplained hereinafter.

The machine operates in the following manner:

Initially, the motor-speed reducer units 23 and 2% are inoperative andthe unit 28 is first started up by closing the switch 37. This unitdrives the driving rollers of the device G continuously and the sheet tis positively fed tangentially to the anvil 4 in the direction of arrowf until the end transverse edge of the sheet is engaged between theefiective face 11 of the guide block it? and the anvil 4. At thismoment, the motor-speed reducer unit 23' is started up so as to impartto the punch 13 an alternating rectilinear motion on the axis YY whilethe sheet 2. is continued to be positively fed in a continuous manner.Thus the length of the sheet 2 between the anvil 4 and the point whereit leaves the feed-device G is caused to exceed said distance L, sinceit does not yet issue from the bending device of the machine at the samerate as its feed to the anvil and is therefore elastically deformed by awarping C whose deflection is about cm. for a 2 mm. thick sheet. Whenthe punch 13 strikes the sheet t it applies it against the anvil 4 asshown in FIG. 4 and permanently deforms it at-zb, whereas it elasticallyupwardly displaces at bed the excess sheet not yet engaged between theanvil and the punch. Thisv excess sheet is therefore. buckled or warpedalong the bend C whose convex face abcd is directed toward the anvil 4and whose radius of curvature is greater than that of the effective faceof the anvil, so that the deformation ofthe sheet along this bend isonly temporary. When the punch once more descends to the position 13ashown in dot-dash line (FIG. 4), the temporary bend: C tends tostraighten under the efiiect of elasticity, as shown ta C and forces theportion of sheet just bent at abto ad- Vance between the anvil 4 and theguide block and coil roundthe anvil This procedure isrepeated: for eachstroke of the punch and in this way the sheet is permanently bent littlebylittle.

'Owing to this arrangement, the bend C tends to apply the sheet. againstthe anvil, which favours the permanent bending. Further,v owing to itselastically straightening.

out, the bend. Cl supplies the energy for coiling the sheet round theanvil. This bend is also a sheet accumulator. and a connecting meansbetweenthe continuous feed device G. and the discontinuous bendingdevice (413'). This bendC permits the motor-speed reducer unit 28 of thefeed. device G to. operate, in a simple manner independently of themotor-speed reducer unit 23 driving the punch, without anysynchronisation therebetween.

'As each coil of sheet is being formed after application of the sheet 2against the anvil 4, this coil taking up. position. adjacent thepreviously-formed coil, both adjacent coils are welded together by aseriesof spaced spot welds, each spot weld being produced simultaneouslywith the operative stroke of the. punch 13 toward the anvil 4 owing tothe action of the electrodes 24 and 25, Whose current supply is,controlled by the device drivingthe punch through the medium of thecontactor 26. The tube T is thereby produced.

Owing to the inclination ofthe coils relative to the axis XXcorresponding to the angle y, the tube T, which is subjected to thethrust of the sheet I under elastic stress in the bend C, undergoes anintermittent helical movement and, without any special driving device,progresses longitudinally along the axis XX in a discontinuous manner asnew coils are formed. If the blows of the punch are repeated veryquickly (for example 300 blows per minute) and the sheet is fed to theanvil slowly (for example 10 mm. per blow), the movement of the tube outof the machine is substantially continuous, which permits application ofany continuous welding devices for performing the final Welding of thetube.

Owing to the combination of the guide block 10 and the anvil 4, thecoils de not have a tendency to uncoil themselves or to increase indiameter in a more or less controllable manner, which occurs when asheet elastically straightens itself out and increases its radius ofcurvature when it is once more released after having been subjected to abending force. In the present invention, the sheet is trapped betweenthe anvil 4 and the guide block 10 and is made to conserve the radius ofcurvature that the punch imparted thereto when it applied the sheetagainst the'anvil. Thus the coils have a constant diameter which iscontrolled with great accuracy and the formed tube T undergoes itshelical movement while its axis remains fixed in a precise manner, whichfacilitates the subsequent finishingand handling operations on saidmachine. Further, the machine functions in an improved manner, since itis only subjected to the vibration-of hardly any etfect on themachineemanating from the sheet as it rises and tends to straighten outin the bend C within a predetermined constant length.

Furthermore, owing to the fact that the spot welding is carried out onthe part of the tube which is already permanently bent, the spot weldsare not subsequently subjected to any stress, which permits welding in arather superficial and therefore rapid manner, thereby accelerating therate of the blows of the punch and increasing the production capacity ofthe machine.

Finally, the safety contactor (29--33) located over the region in whichthe sheet t is fed to the machine so as to act as means limiting themaximum amplitude of the band C, is adapted to open the supply circuitof the motorspeed reducer unit 28 when, for any reason, the rate ofcoiling the sheet 2 round the anvil 4 becomes less than that of its feedtoward the machine and the surplus length of sheet becomes excessive andthe amplitude of the bend C exaggerated. In this event, without thecontactor (291-33) there would be a danger that the deformation of thesheet in the bend be permanent, which must be avoided.

Similarly, the safety contactor (30-34) located below the sheet If andacting as means limiting the minimum amplitude of the bend C, is adaptedto open the supply circuit of the motor-speed reducer unit 23 if for anyreason. the rate of feed of the sheet becomes less than that of itscoiling round the. anvil 4. In this way, the deflection of the bendcannot diminish to a point. at which the resulting increased tension ofthe sheet is capable of opposing its application against the anvil underthe effect of the punch.

In both cases, the supply current of the circuit for the units 28 and 23is re-established assoon as the bend C leaves the abutments 29 and 30.

In a modification shown'in FIG. 5, the offset x between the anvil 4 andthe working axis Y--Y of the punch is adjustable. To this end, the punch13a is movable along the plate 15 in a direction perpendicular to theaxis XX owing to provision of a dovetail arrangement 39.and an adjustingscrew 49 co-acting with a nut 41 mounted on the plate 15.

Further, the guide block 10a has a plane or slightly convex efiectiveface. and is capable of being shifted in a direction perpendicular tothe axis XX by means of a dovetail arrangement: 42 provided on the table3" and an adjusting screw 43 coacting with a nut 44 mounted on the table3. By means of this arrangement, the same punch and the same guide blockcan always be used, even when the diameter and/or the thickness of thepipe to be produced vary. It is merely necessary to move the punch andthe guide block away from the anvil when the diameter and/or thethickness of the pipe increase, and to move them toward the anvil in theopposite case.

Although specific embodiments of the invention have been described, manymodifications and changes may-be made therein without departing from thescope of the invention as defined in the appended claims.

Thus, instead of arranging that the device G be orientatable for thepurpose of varying the angle y between the feed direction h of the sheetand the axis X--X, the device G could be fixed in position and themachine be made orientatable about a pivot connected to the stand of themachine.

Having now described my invention What I claim as new and desire tosecure by Letters Patent is:

l. A method of bending a sheet about a cylindrical portion of a fixedform, comprising: continuously positively feeding the sheet in thedirection toward said form, maintaining the sheet free of restrictionover a determinable length prior to its reaching said cylindricalportion of the form, applying to the free length of the sheet adiscontinuous force substantially perpendicular to said sheet forpermanently bending a portion of said sheet by applying the latteragainst the cylindrical portion of the form, said portion facing thedirection from which the sheet is fed, and creating simultaneously insaid free length of sheet, upstream of the sheet portion which is beingpermanently bent and which is temporarily stopped due to its beingapplied against the form, due to the continuous positive feed of thesheet toward said form, an elastic bend whose convexity is directedoppositely to that of said sheet portion, then terminating the bendingforce so that the potential energy stored in said elastic bendautomatically and simultaneously causes the expansion of said elasticbend and an advance with respect to said form of the permanently bentsheet portion, and guiding said bent sheet portion during its advanceabout the fixed form on the downstream side thereof opposite thedirection of feed of the sheet with respect to the form.

2. In a machine for bending a metal sheet, in combination: a fixed form,at least a part of the surface of which is cylindrical, a feed devicefor continuously positively feeding the sheet to be bent in thedirection toward said form and spaced a determinable distance from saidform so that a corresponding length of the sheet is freely located inspace between said form and said feed device, pushing means offset withrespect to the form on the side of said form facing the feed device toexert on said free length of sheet upstream of said form discontinuoussuccessive bending forces substantially perpendicular to said length ofsheet, and a device for guiding the sheet which is bent around the fixedform by said pushing means, said guide device, being located on thedownstream side of the form facing away from the feed device.

3. A method of forming a helical sheet winding by bending said sheetabout a fixed anvil having a cylindrical surface, said method comprisingcontinuously feeding the sheet to be bent to said anvil along an obliquedirection relative to the generatrices of said cylindrical surface andin such a manner that a certain length of sheet is freely located inspace before reaching said cylindrical surface;

' 6 applying successive and discontinuous blows on the portion of thesheet located immediately above the anvil in said free length so as toapply said portion, upon applition of each blow, against said anvil on aportion, facing the side from which the sheet is fed, of the cylindricalsurface of said anvil, while forming an elastic bend in said sheetimmediately above said portion of the sheet applied against the anvil,in such a manner that the elastic bend automatically causes, by itsexpansion after application of the blow, the peripheral advance of thepermanently bent portion of the sheet relative to the anvil, and guidingsaid bent portion. of the sheet around said anvil on the side oppositethe feeding of the sheet relative to the fixed anvil. 1

4. A machine for helically winding a metal sheet, comprising incombination: a stand; an anvil having a fixed axis carried by said standand having an at least partially cylindrical surface; a feed device forcontinuously feeding the sheet to be bent to said anvil, said feeddevice being located at a determinable distance from the anvil so as toleave a determinable length of sheet freely located in space betweensaid anvil and said feed device, and being disposed in such a mannerthat the sheet reaches the anvil along a direction which is oblique tothe generatrices of the cylindrical surface; a bending device carried bysaid stand for applying on the free length of sheet discontinuoussuccessive forces perpendicular to said free length for permanentlybending the free part of sheet adjacent said cylindrical surface of theanvil and elastically bending the rest of said free part of the sheetadjacent the feed device, said device comprising a punch provided with aconvex working end and movable along an axis which is orthogonal to theaxis of the anvil and offset relative to said anvil axis toward the sideof the feed device, guide means for guiding said punch along its axis onsaid stand, and a mechanism for imparting to said punch a reciprocatingmovement along said punch axis; and a guide block for guiding theportion of sheet bent by said bending device round the cylindricalsurface of the anvil, said block being supported by said standconcentrically to said cylindrical surface on the side opposite the feeddevice relative to the anvil and defining with the latter a narrowpassage concentric to said cylindrical surface of the anvil.

5. A machine as claimed in claim 4, wherein said punch is movabletransversely of its axis on said guiding means, and comprising anadjusting device connecting said punch to said guiding means foradjusting the position of said punch transversely on said guiding meansand, thus, with respect to the anvil.

6. A machine as claimed in claim 4, wherein said guide block for thebent sheet is movable relative to said anvil, comprising an adjustingdevice which connects said guide block to said stand for displacing saidguide on said stand relative to said anvil.

References Cited in the file of this patent UNITED STATES PATENTS392,598 Farnum Nov. 13, 1888 2,264,800 Hartsman Dec. 2, 1941 2,303,143Spangler Nov. 24, 1943 2,343,899 Groll et al Mar. 14, 1944 FOREIGNPATENTS 549,772 'Italy Oct. 17, 1956 556,229 Great Britain Sept. 24,1943

